The use of synthetic surfactants in cleansing products is well known. For example, U.S. Pat. Nos. 2,970,963, 2,970,964, 2,979,465, 2,988,511, 2,989,547, and 2,999,068 disclose the incorporation of alkyl glycerol ether sulfonates (AGES) in cleansing products such as household dishwashing detergent, cream shampoo and detergent bars. The formula for AGES is: ##STR2## where R=C.sub.8 -C.sub.20.
It is known to use AGES in shampoos and soaps, as evidenced by U.S. Pat. Nos. 3,247,121, 3,980,769, 4,217,296, 4,244,840, 4,327,334, 4,491,539, 4,491,539, 4,636,329, and 4,678,606. Furthermore, U.S. Pat. No. 2,999,068 to Pilcher teaches that ethylene oxide polymers can be added to an AGES composition to provide lubricity to the lather of a soap bar. Also U.S. Pat. No. 4,554,098 to Klisch teaches that polyethylene oxide may be added to liquid detergents (e.g., sulfonates) to reduce skin irritation.
The prior art also teaches the use of ethoxylated surfactants. For example, U.S. Pat. No. 4,578,216 to Fujii teaches the use in shampoos of "polyoxyalkylene alkyl ether sulfates" having the formula: EQU RO(CH.sub.2 CH.sub.2 O).sub.n --SO.sub.3 X
where X may be Na. Also U.S. Pat. No. 5,028,353, entitled "Combination Detergent and Soap Bar", assigned to the assignee of the present application, teaches the use of AEOS (alpha ethoxy olefin sulfonate) in soap bars. Finally, U.S. Pat. No. 4,877,546 to Lai, assigned to the assignee of the present application, discloses a surfactant system useful in hard surface cleansing systems comprising "alkyl ethenoxy ether sulfate" having the same formula: RO(CH.sub.2 CH.sub.2 O).sub.n --SO.sub.3 X.
However, ethoxylated surfactants are not readily processable into soap bars at high levels. For example bars with even as low as 2-3 wt % ethoxylated surfactant usually present processing problems. Generally 2-5 wt % ethoxylated surfactants present very significant problems and where such bar can be produced it is often of a soft and sticky nature.
None of the above-discussed prior art discloses the use of the sodium salt of alcohol ethoxy glyceryl sulfonate (manufactured under the trade name NEGS from Shell Chemical Company) in a cleansing product for human use. A patent which discloses the use of NEGS, i.e., U.S. Pat. No. 4,502,538 to Wellington, relates to the recovery of oil underground.
Fatty acid soaps have been widely employed and known for many years as effective general all purpose cleaning agents. However, the use of fatty acid soaps with hard water gives rise to the formation and precipitation of insoluble fatty acid salts commonly referred to as lime soaps. These precipitated lime soaps tend to coagulate and form a curd in wash basins, bath tubs and the like where the lime curd rises to the surface of the water and adheres to the wash basin or bath tub in the area of the water line. It is this precipitation and attachment of lime soaps to wash basin and bath tubs that produces the familiar ring on bath and basin surfaces. These lime soaps may also leave a film and a feeling of tightness on the skin after washing in hard water with fatty acid soaps. Consequently, various efforts have been undertaken to solve the lime soap curd formation by adding curd dispersants or using synthetic surfactants in place of all or part of the fatty acid soap.
The use of synthetic surfactants in place of fatty acid soaps eliminates the need for a dispersant because no lime soap curds will be formed by the synthetic surfactant in hard water. However, synthetic surfactants are more expensive than fatty acid soaps and synthetic surfactants can be irritating to the skin. By the term mild, it is meant the skin feel of the soap both during and after usage. The problem results from various groups on the surfactants forming salt-like linkages with the epidermis of the skin. Owing to this, the outer layers of the epidermis lose their elasticity, becoming cracked and prematurely rubbed off, which causes a sticky, stretched or burning sensation in the skin of the persons affected and leads to itching. It is also a factor that when a soap bar is comprised completely of a surfactant with no fatty acid soap, it is difficult to form the composition into bars.
Further, surfactants will tend to absorb moisture, swell and have a tendency to crack.
There are yet other properties that are necessary for a good soap composition. Besides being mild and not forming lime soap curd, the soap should also exhibit good lather performance. The use of anionic surfactants can yield a high lather volume, but again such surfactants have a fairly high degree of harshness with resulting skin irritation. When anionic surfactants are utilized, efforts to decrease the degree of harshness consist of adding to the soap composition substances such as moisturizers and fatty acids. However, these various additives then present other problems. When fatty acids are added to the soap compositions, there then results the potential problem of rancidity of the soap composition during a period of extended storage. The use of moisturizers can also create problems. For instance, moisturizers can leave the skin with a greasy filmy feeling as the skin dries. Such a skin feeling is opposite to that which is normally associated with clean skin.
The problem of reducing skin irritation also applies to other skin cleansing products, such as shampoos, liquid soaps, bubble baths and shower gels, containing anionic surfactants.